The Wall Street Journal made the discovery while examining a 50,000-page archive complied by Wallenberg’s half-brother, Guy von Dardel. The archive includes a diary kept by Wallenberg’s mother Maj von Dardel and stepfather Fredrik von Dardel, and a collection of letters, interviews and other documents relating to the search for Wallenberg.

Wallenberg was a Swedish diplomat who, with the backing of the United States, saved the lives of tens of thousands of Hungarian Jews from Nazi death camps in 1944–45. On Jan. 17, 1945, he was arrested by Soviet troops on suspicion of being a U.S. spy and taken to Moscow.

Though his arrest violated international law, the Swedish government did little to secure Wallenberg’s return. The von Dardels pressed the Soviet government for answers, but received conflicting reports that he was dead, in various prisons or unknown to the Soviet government.

In 1956, the von Dardels wrote a letter to Wallenberg. “The 11 years which have passed since your disappearance have been filled with despair day and night, but we have been sustained by the hope of one day seeing you among us and again being able to kiss you and hold your hands and hear your beloved voice,” they wrote.

In 1957, the Soviet government revealed that Wallenberg died of a heart attack in Moscow’s Lubyanka prison in July 1947, but few believed the report. The von Dardels kept hoping that their son was alive and continued to search.

In 1979, a Swedish paper reported that Wallenberg had been seen alive in a Russian prison as late as 1975, but the report was shown to be false. Soon after, on Feb. 12, Mr. von Dardel overdosed on prescription drugs and died. Two days later, Mrs. von Dardel did the same.

Guy von Dardel and Lagergren have continued the search for their brother, but they have given up hope that he is alive. “Now that the toll of Raoul Wallenberg’s disappearance on his family is known, perhaps Russia and Sweden can come together and provide them some answers while they’re still alive,” says Joshua Prager, author of The Wall Street Journal piece.

Raoul Wallenberg was born Aug. 4, 1912, in Stockholm, to a distinguished family. He studied in the United States and worked commercially in South Africa, Palestine and Central Europe. In 1944, though he had no diplomatic experience, he was recruited by the U.S. War Refugee Board to lead a mission to save Jews in Hungary.

Wallenberg arrived in Budapest on July 9, 1944, as first secretary of the Swedish Legation. Deportations had been temporarily halted, leaving Budapest’s nearly 200,000 Jews safe for the time being.

Wallenberg issued Swedish passports, which he had printed in blue and yellow with Sweden’s Three Crowns prominently displayed to attract respect from Hungarian authorities. He was originally allotted between 1,000 and 1,500 of these passports, but he persuaded the Hungarian Foreign Ministry to allow 4,500. Wallenberg is estimated to have issued three times as many by creating thousands of counterfeit passports with the help of over 300 Jewish volunteers.

He also established hospitals, nurseries, soup kitchens and other “safe houses” under the authority of the Swedish Legation and decorated with Swedish flags. He was able to hide between 15,000 and 20,000 Jews inside these 32 safe houses.

Wallenberg’s effort inspired delegates from other neutral nations, including Switzerland, Spain and Italy, to issue visas and establish safe houses.

In October 1944, the Hungarian Nazi Arrow Cross seized power and resumed deportations by foot, forcing Jews to march 120 miles to the Austrian border. Wallenberg accompanied some of the “death marches,” handing out food and medicine. He also convinced Nazi guards through threats and bribes to release marchers with Swedish passports.

When Budapest was liberated by the Soviet Union in February 1945, nearly 100,000 of the original 200,000 Jews were still alive.